Paper ICF100893OR Hydrogen, Hydrides, and Crack Tip Deformation in Titanium C.L. Briant, Z.F. Wang, and K.S. Kumar Division of Engineering Brown University Providence, RI 02912 USA ABSTRACT This paper summarizes results obtained in our laboratory on the susceptibility of commercial purity titanium and the α/β titanium alloy Ti-5111 to hydrogen cracking. The tests were run under cathodic polarization in sodium chloride solutions. Cathodic potentials as low as –1400mVSCE had little effect on the mechanical properties of grade 2 titanium, but grade 3 titanium showed a decrease in the elongation to failure as the electrochemical potential became more cathodic. However, the fracture mode remained ductile with microvoids nucleating at hydrides. Ti-5111 was very susceptible to hydrogen cracking when the pH of the solution was low and the electrochemical potential was cathodic, but hydrides did not appear to play a role in the cracking process. KEYWORDS titanium, hydrogen embrittlement, sodium chloride solutions, Ti-5111 INTRODUCTION The mechanisms of hydrogen embrittlement have been a topic of great debate in past years. One reason for this is that the actual mechanism can vary significantly from one materials system to another [1]. In some materials, such as titanium and zirconium, the primary cause of embrittlement appears to occur through hydride formation. In other materials, such as steel and nickel-base materials, atomic hydrogen appears to be the primary cause of embrittlement. More recent studies of intermetallic compounds have suggested that the source of hydrogen is very important [2]. For example, in FeAl the presence of atomic hydrogen in the environment does not appear to have a great effect on mechanical properties, whereas water vapor can cause a significant decrease in elongation to failure. Although one single mechanism will not explain hydrogen embrittlement, it is important to have complete descriptions of this problem in all important structural materials. We have recently examined hydrogen embrittlement in various grades of
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